1. Field of the Invention
The present invention relates to a semiconductor package, and more particularly, to a high power semiconductor package generating a lot of heat.
2. Description of the Related Art
Electric power devices, for example, silicon-controlled rectifiers (SCRs), power transistors, insulated-gate bipolar transistors (IGBTs), MOS transistors, power rectifiers, electric power regulators, inverters, converters, or high power semiconductor chips combining the above listed devices are designed to operate within a voltage range of 30V through 1000V or higher. The high power semiconductor chips operate at high voltages unlike low power semiconductor chips such as logic devices or memory devices, and thus, generally are required to have a high heat dissipation efficiency for dissipating heat generated from the high power semiconductor chip and also to have a high electrical insulation property under high operational voltages.
FIG. 1 is a cross-sectional view of a conventional high power semiconductor package 100.
Referring to FIG. 1, a substrate 40 in the high power semiconductor package 100 can include a base metal layer 10 for transmitting the heat to a heat dissipation plate 80, a base electrical insulation layer 20 formed on the base metal layer 10, and a conductive pattern 30 formed on the base insulation layer 20. A high power semiconductor chip 50a and/or a low power semiconductor chip 50b can be mounted on the substrate 40. An insulation member 52 for insulating the conductive pattern 30 from the low power semiconductor chip 50b can be disposed between the conductive pattern 30 and the low power semiconductor chip 50b. 
Wire bonding pads 51 that are electrically connected to corresponding conductive patterns 30 can be formed on the high power semiconductor chip 50a and the low power semiconductor chip 50b. 
In general, the wire bonding pads 51 of the high power semiconductor chip 50a and the low power semiconductor chip 50b are electrically connected to the conductive patterns 30 by bonding wires 70. After the wire bonding process, the conductive patterns 30 are connected to leads 60 which form external terminals of the semiconductor package 100 and the high power semiconductor package 100 is completed by performing a transfer molding process using a molding material such as an epoxy molding compound (EMC).
In general, the high power semiconductor package 100 generates a lot of heat during operating, and thus, the heat dissipation plate 80 is attached onto the base metal layer 10. The heat dissipation plate 80 is generally formed of a metal having superior thermal conductivity. The heat dissipation plate 80 can be attached onto the base metal layer 10 using an attachment member 85 such as a heat-resistant grease.
FIG. 2 is a schematic side view illustrating a circuit for electrical insulation testing of the high power semiconductor package 100 of FIG. 1.
The high power semiconductor chip 50a operates at the high voltage, for example 600V or higher, in a normal operation mode, and the base electrical insulation layer 20 that insulates the conductive patterns 30 from the base metal layer 10 is required to have high voltage electrical insulating properties. In order to evaluate the insulation property of the base insulation layer 20, the high power semiconductor package 100 undergoes the electrical insulation tests.
When the heat dissipation plate 80 is attached to the high power semiconductor package 100, the electrical insulation test can be performed by checking whether an electric current flows between the heat dissipation plate 80 and the leads 60 while applying a high voltage between the heat dissipation plate 80 and all of the leads 60 that protrude from the semiconductor package 100. However, since usually the heat-resistant grease 85 is an electrical insulator, the above electrical insulation test cannot reflect the insulation property of the base insulation layer 20 exactly.
In addition, it may sometimes be desirable to electrically connect together the base metal layer 10 and the heat dissipation plate 80 and have the heat dissipation plate 80 grounded in order to provide the high power semiconductor package 100 with an external ground for attenuating electrical noise. However, for the package 100 shown in FIG. 1, it may be difficult to provide the base metal layer with the reliable external grounding if the heat-resistant grease 85 has electrical insulating properties.